Centrifugation
How can you work out centrifugal force?
CF = mass.w^2.x Mass = Mr/N (avogadro's number). Therefore, CF= (Mr/N).w^2.x.
What is a centripetal force?
A force that acts towards the centre of the axis of rotation. This keeps a body moving in a circle.
What is centifugal force?
A force, arising from the body's inertia, which appears to act on a body moving in a circular path and is directed away from the centre around which the body is moving.
What is analytical (characterisation) chromatography?
A way to discover the molecular weight of a macromolecule, density, shape, conformational change, association/dissociation.
What information can be obtained from sedimentation velocity?
- Biomolecular Shape - Biomolecular Conformational Changes - Assembly and Disassembly of Biomolecular Complexes - Molecular Mass and Subunit Stoichiometry - Equilibrium Constants for Self-Associating Systems.
What information can be determined from sedimentation equilibrium?
- Molecular mass and sub unit stoichiometry - Equilibrium constants for hetero-associating systems - Equilibrium constants for self associating systems
What is preparative (isolation) chromatography?
Whole cells, cell components (organelles, membranes, nuclei), sub cellular components (macromolecules) are collected in a pellet at the bottom of a solution.
What is sedimentation velocity?
An analytical ultracentrifugation method that measures the rate at which molecules move in response to centrifugal force generated in a centrifuge. This sedimentation rate provides information about both the molecular mass and the shape of molecules.
What are the 4 principles of the Svedburg equation?
1) Centrifugal force 2) Buoyancy effect 3) Resultant force 4) Velocity produced
What does the rate of a particle in sedimentation in a centrifuge depend on?
1) Speed of spinning 2) Mr of particle 3) Shape and size of particle 4) Solvent properties, e.g. viscosity 4) Size of centrifuge
What is Newton's second law?
Force = Mass x Acceleration (F=MA). This equation can be changed into: r = M(w^2)x, where M = mass, x = distance of object from axis of rotation, and W = angular velocity (radians/sec).
What are the two types of chromatography?
Preparative chromatography - cells/pellet. Analytical chromatography - determines the mass, shape and structure of the particle.
How do you work out resultant force?
RF = CF - UF. RF = m/N.w^2.x - (mρ0/Nρp)w^2.x Therefore, RF = m/N.w^2.x(1-ρ0/ρ)
How do you work out velocity produced?
The resultant force produces a particle velocity. Velocity is proportional to the force applied. dx/dt is proportional to the resultant force, where x=distance from axis, and t=time. Therefore, RF=f∙(dx/dt), where f is the frictional coefficient (a shape factor).
How do analytical centrifuges work?
They have a preparative ultracentrifuge and an optical detection system. This can measure sample concentration inside the centrifuge cell during or after sedimentation.
How can you work out buoyancy (Archimedes principle)?
Upthrust force (weight of solvent displaced) = Mass of solvent.w^2.x. Mass = VoPo (vol. and density of solvent). UF= Voρo.w^2.x Vo = Vp (volume of particle) Vp = m/Nρp (ρp is density of particle) UF = (mρ0/Nρp)w^2.x
What is the equation to work out mass from resultant force?
m/N w^2x (1-ρ0/ρp) =f∙(dx/dt). Therefore, m = fN((dx/dt)/w^2x) / (1-ρ0/ρp). (dx/dt)/w^2x = S. 1/ρp = ṽ (partial specific volume) vol = mass/ρ therefore ṽ=1/ρp (i.e. ṽ is a volume occupied by 1 g of solute) f = RT/ND (D=diffusion coefficient, R = gas constant, T=temp in kelvin).
What are the units for the Svedburg equation?
m=RTs/D(1-ṽρ0) m - kg R - J K-1 M-1 T - K s - s D - m2 s-1 ṽ - mL g-1 ρ - g cm-3
What is the simplified Svedburg equation?
m=RTs/D(1-ṽρo)
